There has hitherto been proposed an on-vehicle speaker system in which a sub-speaker is installed at a sound pressure node (e.g., Patent document 2). Further, there has been proposed a speaker apparatus in which a speaker unit is provided at a position facing a node in a minimum resonant standing wave of a baffle plate (e.g., Patent document 2).
There has also been proposed a technique in which an opening is formed in the side surface on the door hinge side of a speaker box of an automotive door speaker stored in a door by attaching a speaker body to a door inner panel (e.g., Patent document 3). In the present technique, an opening communicating with the opening is formed in a door side panel on the vehicle forward side of the door, and an opening, which communicates with the opening in the door side panel at the time of closing the door, is provided in a cowl side panel on the vehicle backward side of a cowl side communicating with a space in a rocker on the bottom surface. A bass reflex port which communicates the space of the cowl side with the inside of a cabin is provided in the cowl side panel on the cabin inner side of the cowl side. [Patent document 1] Japanese Utility Model Laid-Open No. 1-59388 [Patent document 2] Japanese Patent Laid-Open No. 2008-131199 [Patent document 3] Japanese Patent Laid-Open No. 8-253082 [Patent document 4] U.S. Pat. Laid-Open No. 2009/0279733 [Patent document 5] Japanese Patent Laid-Open No. 2009-1181812 [Patent document 6] Japanese Utility Model Laid-Open No. 5-82195 [Patent document 7] Japanese Patent Laid-Open No. 6-1184